merge revision(s) 39286,39287:

	* ext/psych/lib/psych/y.rb: Document Kernel#y by Adam Stankiewicz
	  [Github tenderlove/psych#118]
	  [Github tenderlove/psych#127]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39582 b2dd03c8-39d4-4d8f-98ff-823fe69b080e